Composition for insulating ceramics and insulating ceramics using the same

ABSTRACT

An insulating ceramic composition includes a mixture of a ceramic powder containing MgAl 2 O 4  and a glass powder containing 30-60% by mole of silicon oxide on the basis of SiO 2  and 20-55% by mole of magnesium oxide on the basis of MgO, and the ceramic powder further includes Mg 2 SiO 4  and TiO 2 . The insulating ceramic composition can be fired at 1000° C. and co-sintered with Ag and Cu. An insulating ceramic obtained by sintering the insulating ceramic composition has a high Q-factor and is therefore suitable for ceramic multilayer substrates used at high frequencies.

TECHNICAL FIELD

The present invention relates to insulating ceramic compositions usedfor, for example, multilayered circuit boards. The present inventionparticularly relates to an insulating ceramic composition that issuitable for a composite multilayered circuit board for mountingsemiconductor elements and various electronic elements and is capable ofbeing fired together with conductive materials such as copper andsilver; an insulating ceramic, a ceramic multilayer substrate, and aceramic electronic component that are produced by sintering aninsulating ceramic composition; and a method for manufacturing a ceramicmultilayer substrate.

BACKGROUND ART

Recently, electronic devices having high-speed processing performancesand using higher frequencies have been increasing and thereforeelectronic components used for such electronic devices must also havehigh-speed processing performances and use higher frequencies. Since theminiaturization of electronic devices has been advancing, electroniccomponents must be miniaturized and mounted in high density.

In order to meet such requirements, multilayered circuit boards formounting semiconductor elements and various electronic elements areemployed. In such multilayered circuit boards, conductor circuits andelectronic functional elements are arranged in a substrate, andtherefore electronic components can be miniaturized.

A principal material for the multilayered circuit board includesaluminum. Since the firing temperature of aluminum is 1500-1600° C.,refractory metals such as Mo, Mo—Mn, and W must be used for conductormaterials of circuits contained in alumina multilayered circuit boards.However, there is a problem in that such refractory metals are expensiveand have a high electrical resistance.

Therefore, there is a large demand for using an inexpensive metal, forthe conductor materials, having a smaller electrical resistance thanthose of the above refractory metals, wherein the inexpensive metalincludes, for example, copper. For example, in Japanese UnexaminedPatent Application Publication No. 5-238774, in order to realize the useof copper for the conductor materials, a substrate material such as aglass ceramic and crystallized glass which are capable of being fired at1000° C. or less is proposed. In Japanese Unexamined Patent ApplicationPublication No. 8-34668, in consideration of the connection tosemiconductor devices such as Si chips, the application of a ceramichaving a thermal expansion coefficient close to that of Si tomultilayered circuit board materials is proposed. However, there is aproblem in that such substrate materials have a small mechanicalstrength and a small Q-factor and that the kinds and the ratio ofdeposited crystal phases are affected by the firing process.

Chip components such as semiconductor devices are mounted on ceramicmultilayer substrates including an insulating ceramic composition insome cases. On the other hand, ceramic multilayer substrates having chipcomponents thereon are mounted on circuit boards such as printed circuitboards for ceramic electronic components. Thus, input/output terminalsfor inputting/outputting signals are essential for such ceramicelectronic components and the distance between the input/outputterminals must be small due to the miniaturization of electroniccomponents.

Therefore, insulating ceramics produced by firing insulating ceramiccompositions must have high dimensional accuracy. However, insulatingceramics produced by firing conventional insulating ceramic compositionshave insufficient dimensional accuracy.

The present invention has been made in order to solve the aboveproblems, and it is an object of the present invention to provide aninsulating ceramic composition (1) that is capable of being firedtogether with a low-melting conductive material such as silver andcopper and (2) that can provide an insulating ceramic having a smallrelative dielectric constant, excellent high-frequency characteristics,and a relatively high thermal expansion coefficient.

It is another object of the present invention to provide an insulatingceramic that is obtained by low-temperature firing and has a smallrelative dielectric constant, excellent high-frequency characteristics,and a relatively high thermal expansion coefficient.

It is another object of the present invention to provide a ceramicmultilayer substrate and ceramic electronic component including aninsulating ceramic composition according to the present invention andhaving excellent high-frequency characteristics and a high-densitycircuit pattern.

It is another object of the present invention to provide a method formanufacturing a ceramic multilayer substrate that can be obtained bylow-temperature firing and has excellent high-frequency characteristicsand dimensional accuracy and in which a high-density circuit pattern canbe formed.

DISCLOSURE OF INVENTION

The present invention provides an insulating ceramic composition (hereinreferred to as a first insulating ceramic composition of the presentinvention in some cases) including a ceramic powder containing spinel(MgAl₂O₄), a glass powder containing 30-60% by mole of silicon oxide onthe basis of SiO₂ and 20-55% by mole of magnesium oxide on the basis ofMgO, and titanium oxide.

In the first insulating ceramic composition of the present invention,the titanium oxide is preferably contained in the ceramic powder. Thecontent of the titanium oxide is preferably 0.5-15% by weight withrespect to the total ceramic powder and glass powder content.

The present invention provides an insulating ceramic composition (hereinreferred to as a second insulating ceramic composition of the presentinvention in some cases) including a ceramic powder containing spinel(MgAl₂O₄) and a glass powder containing 30-60% by mole of silicon oxideon the basis of SiO₂ and 20-55% by mole of magnesium oxide on the basisof MgO, wherein part of the spinel in the ceramic powder is replacedwith Mg₂SiO₄.

In the second insulating ceramic composition of the present invention,15% by weight or less of the spinel is preferably replaced with theMg₂SiO₄ with respect to 100% by weight of the spinel.

In the first or second insulating ceramic composition of the presentinvention, the glass powder preferably further contains 20% by mole orless of boron oxide on the basis of B₂O₃. The glass powder preferablyfurther contains 30% by mole or less of at least one oxide selected fromthe group consisting of CaO, SrO, BaO, and ZnO. The glass powderpreferably further contains 10% by mole or less of aluminum oxide on thebasis of Al₂O₃. The glass powder preferably further contains 10% by moleor less of at least one alkaline metal oxide selected from the groupconsisting of Li₂O, K₂O, and Na₂O with respect to 100% by mass of theglass powder.

The first or second insulating ceramic composition preferably furtherincludes 3% by weight or less of copper oxide on the basis of CuO withrespect to the total ceramic powder and glass powder content.

In the first or second insulating ceramic composition of the presentinvention, the ratio of the ceramic powder content to the glass powdercontent is preferably 20:80 to 80:20 on the weight basis.

The present invention provides an insulating ceramic produced by firingthe first or second insulating ceramic composition of the presentinvention.

The present invention provides a ceramic multilayer substrate includinga plurality of ceramic layers and a conductive wire disposed on at leastone of the plurality of ceramic layers, wherein the plurality of ceramiclayers include an insulating ceramic layer comprising the insulatingceramic of the present invention.

In the ceramic multilayer substrate of the present invention, theplurality of ceramic layers may further include a dielectric ceramiclayer that is disposed on at least one principal face of the insulatingceramic layer and that has a dielectric constant higher than that of theinsulating ceramic layer.

The present invention provides a ceramic electronic component includingthe ceramic multilayer substrate of the present invention and a circuitelement that is mounted on the ceramic multilayer substrate and iselectrically connected to the conductive wire.

The present invention provides a ceramic electronic component includingthe ceramic multilayer substrate of the present invention and aconductive wire connected to at least one of an inductor and a capacitorwhich are circuit elements.

The present invention provides a method for manufacturing a ceramicmultilayer substrate comprising the steps of layering first greenceramic sheets including the first or second insulating ceramiccomposition of the present invention to prepare a layered body,providing a second green ceramic sheet having a sintering temperaturedifferent from that of the first green ceramic sheets onto at least oneprincipal face of the layered first green ceramic sheets, and firing thelayered body including the first green ceramic sheets together with thesecond green ceramic sheet.

In the method for manufacturing a ceramic multilayer substrate of thepresent invention, preferably, the second green ceramic sheet is notsubstantially sintered at the sintering temperature of the first greenceramic sheets. The layered body including the first green ceramicsheets is preferably fired at 1000° C. or less together with the secondgreen ceramic sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical sectional view of a ceramic multilayer module whichis a ceramic electronic component including a ceramic multilayersubstrate according to the present invention.

FIG. 2 is an exploded perspective view of the ceramic multilayer moduleshown in FIG. 1.

FIG. 3 is a vertical sectional view of a monolithic LC filter which is aceramic electronic component including a ceramic multilayer substrateaccording to the present invention.

FIG. 4 is a perspective view of the monolithic LC filter shown in FIG.2.

FIG. 5 is an illustration showing an equivalent circuit of themonolithic LC filter shown in FIG. 3.

BEST MODE FOR CARRYING OUT THE INVENTION

A first insulating ceramic composition of the present invention includesat least a ceramic powder containing spinel (MgAl₂O₄) and a glass powdercontaining 30-60% by mole of silicon oxide on the basis of SiO₂ and20-55% by mole of magnesium oxide on the basis of MgO, and the ceramicpowder further contains titanium oxide (TiO₂).

In the ceramic powder contained in the insulating ceramic composition,MgAl₂O₄, which is a main component, has excellent high-frequencycharacteristics and a high flexural strength, and TiO₂, which is anauxiliary component, functions as a nucleating agent for acceleratingthe crystallization of glass components. Thus, an insulating ceramichaving the following characteristics can be obtained by firing theinsulating ceramic composition: high strength, an excellenthigh-frequency characteristic, that is, a large Q-factor at highfrequencies.

In the insulating ceramic composition, when the glass powder containsCa, the sintered insulating ceramic composition has a large Q-factorbecause of the precipitation of a crystal with a large Q-factor, but Caremains in glass. In the step of forming external electrodes on theinsulating ceramic by a plating process and the like, when Ca remains inglass, the Ca elutes into the plating solution to make the glassfragile. When the insulating ceramic composition contains TiO₂, the TiO₂reacts with the Ca remaining in the glass having the precipitatedcrystal with a large Q-factor to form CaTiO₃. Therefore, the insulatingceramic composition produced by firing the first insulating ceramiccomposition is improved in plating resistance.

CaTiO₃ has a relatively large thermal expansion coefficient and theprecipitation thereof can be controlled with the TiO₂ content, therebycontrolling the thermal expansion coefficient of the insulating ceramic.Furthermore, since TiO₂ and CaTiO₃ has a negative temperaturecoefficient of a dielectric constant, the temperature coefficient of thedielectric constant of the insulating ceramic can be controlled with theTiO₂ content.

Accordingly, the first insulating ceramic composition of the presentinvention preferably contains 0.5-15% by weight of TiO₂ with respect tothe total ceramic powder and glass powder content. When the TiO₂ contentis less than 0.5% by weight, the temperature coefficient of thedielectric constant becomes an excessively large positive value. Whenthe TiO₂ content is more than 15% by weight, the temperature coefficientof the dielectric constant becomes an excessively large negative value.

In the first insulating ceramic composition, TiO₂ is preferablycontained in the ceramic powder.

A second insulating ceramic composition of the present inventionincludes a ceramic powder containing spinel (MgAl₂O₄) and a glass powdercontaining 30-60% by mole of silicon oxide on the basis of SiO₂ and20-55% by mole of magnesium oxide on the basis of MgO, wherein part ofthe spinel in the ceramic powder is replaced with Mg₂SiO₄.

In the ceramic powder in the second insulating ceramic composition,MgAl₂O₄, which is a main component, has excellent high-frequencycharacteristics and high flexural strength, and Mg₂SiO₄, which is anauxiliary component, has excellent high-frequency characteristics and alarge thermal expansion coefficient. Thus, an insulating ceramic havingthe following characteristics can be obtained by firing the insulatingceramic composition: high strength, excellent high-frequencycharacteristics, and a large thermal expansion coefficient.

In the insulating ceramic composition, 15% by weight or less of thespinel is preferably replaced with the Mg₂SiO₄ with respect to 100% byweight of the spinel. When the substitutional rate exceeds 15% byweight, the flexural strength becomes excessively large.

A dense sintered body (namely, an insulating ceramic) can be obtained byfiring the first or second insulating ceramic composition at,particularly, 1000° C. or less. These insulating ceramic compositionscan be fired together with low-melting metal materials such as copperand silver having a small resistivity to provide ceramic multilayersubstrates and ceramic electronic components including conductive wireswhich have a large conductivity and are suitable for use at highfrequencies.

The glass powder in the first or second insulating ceramic compositionof the present invention must contain 30-60% by mole of silicon oxide onthe basis of SiO₂. When the SiO₂ content is less than 30% by mole, thecrystallinity of a sintered insulating ceramic is lowered to decreasethe Q-factor. In contrast, when the SiO₂ content is more than 60% bymole, the melting point of formed glass is increased and therefore thelow-temperature sintering is not possible.

Furthermore, the glass powder must contain 20-55% by mole of magnesiumoxide on the basis of MgO. MgO has a function of reducing the softeningpoint of glass and therefore the glass powder can be readily prepared.Since MgO is a crystal component of crystallized glass, an insulatingceramic produced by firing the insulating ceramic composition has aprecipitated crystal phase such as an MgO—SiO₂ phase or an MgO—CaO—SiO₂phase including the following MgO phase: forsterite, enstatite,diopside, and monticellite. The insulating ceramic having such a crystalphase has a Qf value of several ten thousands GHz, that is, an excellenthigh-frequency characteristic. When the content of MgO in the glasspowder is less than 20% by mole, an obtained insulating ceramic has asmall Q-factor. In contrast, when the content of MgO is more than 55% bymole, the quantity of the precipitating MgO crystal phase becomesexcessively large. Therefore, an obtained insulating ceramic has lowstrength and the low temperature sintering is not possible.

The glass powder preferably further contains 20% by mole or less ofboron oxide on the basis of B₂O₃. Since B₂O₃ functions as a fusing agentin the step of preparing the glass powder, the glass powder containingB₂O₃ can be readily obtained. When the content of B₂O₃ exceeds 20% bymole, an obtained insulating ceramic has inferior moisture resistanceand weak elution resistance to a plating solution in some cases.

The glass powder preferably further contains 30% by mole or less of atleast one oxide selected from the group consisting of CaO, SrO, BaO, andZnO. These alkaline-earth metal oxides have a function of lowering thesoftening point of glass and therefore the glass powder containing theseoxides can be readily prepared. Since the oxides are crystal componentsof crystallized glass, an obtained insulating ceramic has a precipitatedcrystal phase with a large Q-factor. When the content of the oxides inthe glass powder exceeds 30% by mole, an obtained insulating ceramic hasweak elution resistance to a plating solution and a small Q-factor insome cases.

The glass powder preferably further contains 10% by mole or less ofaluminum oxide on the basis of Al₂O₃. Al₂O₃ has a function of improvingthe chemical stability of glass. When the content of Al₂O₃ exceeds 10%by mole, an obtained insulating ceramic has a small Q-factor and a smallthermal expansion coefficient in some cases.

The glass powder preferably further contains 10% by mole or less of atleast one alkaline metal oxide selected from the group consisting ofLi₂O, K₂O, and Na₂O with respect to 100% by mass of the glass powder.These alkaline metal oxides have a function of lowering the softeningpoint of glass. When the content of the alkaline metal oxide exceeds 10%by mole, an obtained insulating ceramic has a small Q-factor and weakelution resistance in some cases.

The glass powder contained in the first or second insulating ceramiccomposition may include a powder prepared by mixing some glass powdershaving different components and preferably includes another powderprepared by mixing some glass powders having different components tofire the mixture at 700-1400° C. to pulverize the resulting mixture.

The first and second insulating ceramic compositions preferably furthercontain 3% by weight or less of copper oxide on the basis of CuO. Copperoxide has a function of lowering the firing temperature of the first andsecond insulating ceramic compositions. When the content of CuO exceeds3% by weight, the Q-factor is insufficient in some cases.

In the first and second insulating ceramic compositions, the ratio ofthe ceramic powder content to the glass powder content is preferably20:80 to 80:20 on a weight basis. When the content of the ceramic powderexceeds the above ratio, an obtained insulating ceramic has a smalldensity in some cases. When the content of the glass powder exceeds theabove ratio, an obtained insulating ceramic has a small Q-factor in somecases.

According to the present invention, in the first insulating ceramiccomposition, part of MgAl₂O₄ in the glass powder may be replaced withMg₂SiO₄. The second insulating ceramic composition may further containtitanium oxide. The quantity of replaced MgAl₂O₄ and the content oftitanium oxide are as described above.

An insulating ceramic of the present invention is produced by firing thefirst or second insulating ceramic composition described above.Therefore, the insulating ceramic of the present invention has highstrength and excellent high-frequency characteristics.

The insulating ceramic preferably has a Q-factor of 400 or more at ameasuring frequency of 15 GHz particularly. An insulating ceramiccomposition of the present invention can provide an insulating ceramichaving a Qf value of 6000 or more, wherein the Qf value is defined asthe product of 15 GHz and the Q-factor. Therefore, the insulatingceramic composition can provide ceramic multilayer substrates suitablefor use at high frequencies.

A ceramic multilayer substrate of the present invention includes aplurality of ceramic layers and a conductive wire disposed on at leastone of the plurality of ceramic layers, wherein the plurality of ceramiclayers include an insulating ceramic layer comprising an insulatingceramic of the present invention.

In the ceramic multilayer substrate, the plurality of ceramic layerspreferably further includes a dielectric ceramic layer that is disposedon at least one principal face of the insulating ceramic layer and has adielectric constant higher than that of the insulating ceramic layer.That is, the ceramic multilayer substrate includes ceramic multilayersubstrates having an insulating layer comprising the insulating ceramicof the present invention and composite ceramic multilayer substrateshaving an insulating layer comprising the insulating ceramic of thepresent invention and a dielectric layer comprising a dielectric ceramicwith a dielectric constant larger than that of the insulating ceramic.

A ceramic electronic component of the present invention has the ceramicmultilayer substrate of the present invention and a circuit element thatis mounted on the ceramic multilayer substrate and is electricallyconnected to the conductive wire. The ceramic electronic componentincludes module components including the ceramic multilayer substratehaving active elements such as semiconductor devices and having passiveelements such as chip capacitors thereon.

A ceramic electronic component of the present invention may have theceramic multilayer substrate of the present invention and a conductivewire connected to at least one of an inductor and a capacitor. Theceramic electronic component of the present invention includes chipcomponents such as multilayer LC filters including the ceramicmultilayer substrate having inductors and capacitors.

These ceramic electronic components of the present invention preferablyincludes a ceramic element comprising the insulating ceramic and aconductor wire having internal electrodes disposed in the ceramicelement and external electrodes disposed on the ceramic element andelectrically connected to the internal electrodes. The ceramic elementpreferably includes a plurality of ceramic layers, and a ceramic layeris preferably placed between an internal electrode connected to acomponent having a potential and another internal electrode connected toa component having another potential among the internal electrodes toform a capacitor. In the ceramic electronic components, the internalelectrodes may be connected to each other to form an inductor.

A method for manufacturing a ceramic multilayer substrate according tothe present invention includes the steps of layering first green ceramicsheets comprising a first or second insulating ceramic composition toprepare a layered body, providing a second green ceramic sheet having asintering temperature different from that of the first green ceramicsheets onto at least one principal face of the layered first greenceramic sheets, and firing the layered body including the first greenceramic sheets together with the second green ceramic sheet.

Preferably, the second green ceramic sheet is not substantially sinteredat a temperature at which the first green ceramic sheets are sintered.The layered body including the first green ceramic sheets is preferablyfired at 1000° C. or less together with the second green ceramic sheet.A ceramic powder contained in the second green ceramic sheet includesceramics such as alumina, zirconia, and magnesia.

Next, with reference to the drawings, the embodiments of a ceramicelectronic component according to the present invention will now bedescribed.

FIG. 1 is a sectional view of a ceramic multilayer module, which is aceramic electronic component of the present invention, and FIG. 2 is aperspective view thereof.

The ceramic multilayer module 1 includes a ceramic multilayer substrate2. The ceramic multilayer substrate 2 has a composite multilayerstructure in which insulating ceramic layers 3 a and 3 b comprising aninsulating ceramic of the present invention have a dielectric ceramiclayer 4 therebetween, wherein the dielectric ceramic layer 4 comprisesbarium titanate and glass and has a relatively high dielectric constant.

The dielectric ceramic layer 4 has a plurality of internal electrodes 5therein to form capacitors C1 and C2, wherein the plurality of internalelectrodes 5 are each arranged between parts of the dielectric ceramiclayer 4.

The insulating ceramic layers 3 a and 3 b and the dielectric ceramiclayer 4 have a plurality of via-hole electrodes 6 and 6 a and internalwires.

On the other hand, electronic component devices 9 to 11 are mounted onthe ceramic multilayer substrate 2. The electronic component devices 9to 11 include semiconductor devices, chip-type multilayer capacitors,and the like. These electronic component devices 9 to 11 areelectrically connected to the capacitors C1 and C2 to form the electriccircuit of the ceramic multilayer module 1.

The ceramic multilayer substrate 2 has a conductive cap 8 thereon in afixed manner. The conductive cap 8 is electrically connected to thevia-hole electrodes 6 a extending from the upper face to the lower faceof the ceramic multilayer substrate 2. External electrodes 7 aredisposed on the lower face of the ceramic multilayer substrate 2 and areelectrically connected to the via-hole electrodes 6 and 6 a. Otherexternal electrodes, which are not shown, are disposed on the ceramicmultilayer substrate 2 in the same manner as in the external electrodes7. These external electrodes are electrically connected to theelectronic component devices 9 to 11 and the capacitors C1 and C2 withthe above internal electrodes.

Since the external electrodes 7 are disposed on the lower face of theceramic multilayer substrate 2, the ceramic multilayer module 1 can bereadily mounted on a printed circuit board using the lower face.

In this embodiment, since the cap 8 comprises a conductive material andis electrically connected to the external electrodes 7 with the via-holeelectrodes 6 a, the electronic component devices 9 to 11 can beelectromagnetically shielded with the cap 8. However, the conductive cap8 does not necessarily comprise a conductive material.

Since the ceramic multilayer module 1 includes the insulating ceramiclayers 3 a and 3 b comprising an insulating ceramic according to thepresent invention, the dielectric constant is small and the Q-factor islarge at high frequencies and therefore the ceramic multilayer module 1is suitable for high-frequency applications.

The ceramic multilayer substrate 2 can be readily manufactured by aconventional method for co-firing ceramic layers.

That is, green ceramic sheets, having a predetermined electrode pattern,for dielectric ceramic layers are prepared according to the followingprocedure: green ceramic sheets principally comprising a dielectricceramic composition such as barium titanate are provided, and anelectrode pattern for forming the internal electrodes 5, via-holeelectrodes 6 and 6 a, and the like is then printed thereon. Furthermore,other green ceramic sheets, having a predetermined electrode pattern,for insulating ceramic layers are prepared according to the followingprocedure: green ceramic sheets comprising an insulating ceramiccomposition of the present invention are provided, and an electrodepattern for forming the internal electrodes 5, via-hole electrodes 6 and6 a, and the like is then printed thereon.

A predetermined number of the green ceramic sheets for dielectricceramic layers and the green ceramic sheets for insulating ceramiclayers are stacked to form a layered body, and the layered body is thenpressed in the thickness direction. The resulting green layered body isthen fired at a predetermined temperature, thereby obtaining the ceramicmultilayer substrate 2.

FIGS. 3 to 5 are an exploded perspective view, a schematic perspectiveview, and a circuit diagram of a monolithic LC filter, respectively,which is a ceramic electronic component of the present invention.

A monolithic ceramic electronic component 20 shown in FIG. 4 is themonolithic LC filter. A ceramic sintered body 21 has a circuit includingan inductor L and a capacitor C therein, as described below. The ceramicsintered body 21 comprises an insulating ceramic of the presentinvention. External electrodes 23 a, 23 b, 24 a, and 24 b are disposedon the ceramic sintered body 21, and an LC resonant circuit shown inFIG. 5 is placed among the external electrodes 23 a, 23 b, 24 a, and 24b.

A method for manufacturing the ceramic sintered body 21 will be nowdescribed with reference to FIG. 3 to make the configuration thereofclear.

An organic vehicle is added to an insulating ceramic composition of thepresent invention to prepare a ceramic slurry. The resulting ceramicslurry is processed into green ceramic sheets by an ordinarysheet-forming method. The resulting green ceramic sheets are dried andthen punched out to prepare rectangular green ceramic sheets 21 a to 21m having a predetermined size.

Perforations for forming a via-hole electrode 28 are provided in thegreen ceramic sheets 21 a to 21 m depending on needs. Conductive pasteis then provided thereon by a screen-printing process to form conductivecoils 26 a and 26 b for an inductor L1, internal electrodes 27 a to 27 cfor a capacitor C, and conductive coils 26 c and 26 d for anotherinductor L2, and is packed into the perforations to form the via-holeelectrode 28.

Subsequently, the green ceramic sheets 21 a to 21 m are stacked in thedirection shown in the figure and then pressed in the thicknessdirection to form a layered body. The resulting layered body is fired toprovide the sintered body 21.

As shown in FIG. 4, the external electrodes 23 a to 24 b are provided onthe resulting sintered body 21 by a thin-film forming process such asthe application and the baking of conductive paste, vapor deposition,plating, or sputtering. The monolithic ceramic electronic component 20is obtained in the above manner.

As shown in FIG. 3, the conductive coils 26 a and 26 b form the inductorL1 shown in FIG. 5, the conductive coils 26 c and 26 d form the inductorL2, and the internal electrodes 27 a to 27 c form the capacitor C.

In the monolithic ceramic electronic component 20 of this embodiment,the monolithic LC filter has the above configuration. Since the sinteredbody 21 comprises an insulating ceramic of the present invention, thesintered body 21 is sintered at a low temperature in the same manner asin the ceramic multilayer substrate 2 described above. Thus, theconductive pattern 26 a to 26 c and the electrode pattern 27 a to 27 ccomprising a low-melting metal such as copper, silver, or gold can befired together with an insulating ceramic composition. Since themonolithic LC filter includes a conductive material having a smallresistivity and the insulating ceramic having a large Q-factor at highfrequencies, the monolithic LC filter is suitable for use at highfrequencies.

In the above embodiments, an exemplary ceramic multilayer module andmonolithic LC filter are described. However, a ceramic electroniccomponent of the present invention is not limited thereto. The presentinvention can be applied to the following components: various ceramicmultilayer substrates such as ceramic multilayer substrates formulti-chip modules or for hybrid ICs, various ceramic electroniccomponents including a ceramic multilayer substrate having electroniccomponent devices thereon, and various chip-type monolithic electroniccomponents such as chip-type monolithic capacitors and chip-typemonolithic dielectric antennas.

EXAMPLE

The present invention will now be described in detail with reference tothe particular examples.

Example 1

An Mg(OH)₂ powder and an Al₂O₃ powder, which are raw materials, wereweighed so as to form a stoichiometric composition corresponding toMgAl₂O₄ and wet-mixed for 16 hours, and the mixture was dried. The driedmixture was fired at 1350° C. for 2 hours and then crushed. The obtainedpowder was mixed together with a commercially available TiO₂ powder toprepare a ceramic powder.

In order to obtain glass powders having compositions shown in Table 1,raw material powders were mixed in a predetermined ratio to formmixtures, and the mixtures were fired at 700-1400° C. and then crushedto prepare the glass powders having the compositions G1 to G40 shown inTable 1.

The ceramic powder and the glass powders were compounded in the ratiosshown in Tables 2 and 3. A solvent, CuO, a binder, and a plasticizerwere added to these compounds to prepare slurry samples S1 to S51. Theslurry samples were formed into first green ceramic sheets having athickness of 50 μm by a doctor blade method.

Twenty four of the first green ceramic sheets were stacked and thenpressed with a pressure of 2000 kg/cm² to form a cylindrical greenlayered body having a diameter of 12 mm and a thickness of 7 mm.

Apart from the layered body including the first green ceramic sheets, acommercially available aluminum powder that is not sintered at 1000° C.or less was provided for the ceramic powder. The aluminum powder wasmixed together with a solvent, a binder, and a plasticizer to form asecond slurry. The second slurry was formed into a second green ceramicsheet having a thickness of 50 μm by a doctor blade method.

The resulting second green ceramic sheet was cut into pieces having alength of 30 mm and a width of 10 mm. Each second green ceramic sheetpiece was placed on both end faces of the layered body, having the firstgreen ceramic sheets, in the layered direction to press them to form alamination. The lamination, in which the layered body including thefirst green ceramic sheets was sandwiched between the second greenceramic sheet pieces, was fired at 900-1000° C. for 2 hours inatmosphere in such a manner that the layered body including the firstgreen ceramic sheets was sandwiched between the second green ceramicsheet pieces in the layered direction, thereby obtaining a sintered bodyincluding the first green ceramic sheets. Subsequently, the second greenceramic sheet pieces, which were not sintered, were removed to provideinsulating ceramic samples.

For the insulating ceramic samples, the dielectric constant or and theQ-factor were measured at 15 GHz by a dielectric resonator methodshort-circuited at both ends of a dielectric resonator. Furthermore, thethermal expansion coefficient and the difference in dimension of theinsulating ceramic samples were measured.

Separately, the first green ceramic sheets were punched out into pieceshaving a predetermined size. Ag conductive paste was provided on thepieces by a screen printing method to form internal electrodes forcapacitors. The resulting pieces were stacked and then pressed to form alayered body. The layered body was fired at 900-1000° C. to provide aceramic sintered body. Conductive paste was applied onto the ceramicsintered body and baked to form external electrodes. Monolithiccapacitors comprising insulating ceramics having the composition shownin Tables 2 and 3 were obtained in the above manner.

A voltage of 50 V was applied to the monolithic capacitors, and theresulting monolithic capacitors were left in the following conditionsfor 2 hours: a temperature of 120° C., a relative humidity of 95%, and apressure of 2 atm. The change in insulation resistance (TCC) before andafter the high-temperature and high-humidity test was measured toevaluate the moisture resistance. The results are shown in Tables 2 and3.

Sample S0 in Table 2 was prepared by firing the layered body includingthe first green ceramic sheets and not including the second greenceramic sheet pieces.

In the following Table 1, the contents (percent by weight) of Li₂O, NaO,and K₂O are represented with a percentage with respect to the totalamount, 100% by weight, of other glass components.

TABLE 1 SiO₂ MgO B₂O₃ CaO SrO BaO ZnO Al₂O₃ Li₂O K₂O Na₂O (mol %) (mol%) (mol %) (mol %) (mol %) (mol %) (mol %) (mol %) (wt %) (wt %) (wt %)G1 45 55 — — — — — — — — — G2 50 50 — — — — — — — — — G3 30 55 15 — — —— — — — — G4 60 30 10 — — — — — — — — G5 50 40 10 — — — — — — — — G6 5030 20 — — — — — — — — G7 30 50 — 20 — — — — — — — G8 50 20 — — 30 — — —— — — G9 30 45 20 — — — —  5 — — — G10 35 40 10  5  5 — —  5 — — — G1145 50  5 — — — — —  5 — — G12 50 40 — — — — — 10 10 — — G13 40 50 — — —— — 10 10 — — G14 45 40  5 10 — — — —  5 — — G15 45 20  5 — 10 20 — —  5— — G16 35 30 20 — — — 15 —  5 —  5 G17 40 50 10 — — — — —  5 5 — G18 3545  5 15 — — — —  5 — — G19 35 25 10 — — 30 — —  5 — — G20 30 45 15 — — 5  5 —  5  5 — G21 45 25  5  5 —  5  5 10 10 — — G22 35 24 21 — — — 20—  5 — — G23 39 20 21 — — — 20 —  4 — — G24 34 45 21 — — — — — — — — G2540 20 9 — 10 21 — —  5 — — G26 30 30 — 30  5 — —  5 — — — G27 34 20 1031 —  5 — —  4 — — G28 30 20 19 — — 31 — —  5 — — G29 45 24 — — 31 — — —— — — G30 49 40 — — — — — 11 10 — — G31 35 30 10 —  4 — 10 11 — — — G3240 39 10 — — — — 11 — — — G33 40 30 10 10 —  5  5 — 11 — — G34 35 40 10 5 —  5  5 — 11 — — G35 29 55 16 — — — — — — — — G36 51 34 15 — — — — —— — — G37 61 34  5 — — — — — — — — G38 41 19 10 30 — — — —  6 — — G39 4119 20 20 — — — —  6 — — G40 30 56 14 — — — — — — — —

TABLE 2 Ceramic Powder Glass Firing TEC*¹ TCC MgAl₂O₄ TiO₂ Powder CuOTemp. (ppm (ppm DID*² (wt %) (wt %) (wt %) Type (wt %) (° C.) deg⁻¹) εrdeg⁻¹) Q (%) S0 35 5 60 G3 3 900 9.8 6.9 +45 700 0.5 S1 35 0 65 G3 0 90010.2 6.9 +120 400 0.1 (−)*³ S2 35 5 60 G3 3 900 9.9 7.0 +45 730 0.1(−)*³ S3 15 5 80 G18 3 900 9.9 7.0 +60 460 0.1 (−)*³ S4 15 5 80 C18 4900 10.2 7.0 — 160 0.1 (−)*³ S5 15 5 80 G13 3 900 10.6 7.0 +50 460 0.1(−)*³ S6 15 5 80 G5 3 900 9.8 7.0 +50 420 0.1 (−)*³ S7 5 5 90 G5 3 9009.6 6.8 +55 400 0.1 (−)*³ S8 45 5 50 G19 0 900 10.3 7.0 +20 850 0.1(−)*³ S9 45 5 50 G19 1 900 10.4 7.0 +5 880 0.1 (−)*³ S10 55 5 40 G19 0900 10.1 7.1 −5 460 0.1 (−)*³ S11 75 5 20 G19 3 1000 10.5 7.0 −10 4100.1 (−)*³ S12 85 5 10 G19 0 1000 10.6 7.1 +10 400 0.1 (−)*³ S13 45 5 50G26 1 900 10.2 7.1 +10 660 0.1 (−)*³ S14 35 5 60 G26 2 900 9.9 6.9 +20720 0.1 (−)*³ S15 35 5 60 G20 0 900 10.3 7.1 +15 750 0.1 (−)*³ S16 65 530 G20 3 1000 10.7 7.3 −20 420 0.1 (−)*³ S17 35 5 60 G20 3 900 10.3 7.0+5 830 0.1 (−)*³ S18 25 5 70 G20 1 900 10.5 6.9 +40 730 0.1 (−)*³ S19 655 30 G17 3 1000 10.3 7.2 −10 400 0.1 (−)*³ S20 55 5 40 G17 1 900 10.47.1 +5 450 0.1 (−)*³ S21 45 5 50 G17 0 900 10.6 6.9 +10 550 0.1 (−)*³S22 35 5 60 G17 0 900 10.7 6.9 +20 650 0.1 (−)*³ *¹TEC represents theterm thermal expansion coefficient. *²DID represents the term differencein dimension. *³0.1 (−) means 0.1 or less.

TABLE 3 Ceramic Powder Glass Firing TEC*¹ TCC MgAl₂O₄ TiO₂ Powder CuOTemp. (ppm (ppm DID*² (wt %) (wt %) (wt %) Type (wt %) (° C.) deg⁻¹) εrdeg⁻¹) Q (%) S23 35 5 60 G35 3 900 10.3 6.9 — 310 0.1 (−)*³ S24 35 5 60G35 0 1000 9.8 6.9 +30 20 0.1 (−)*³ S25 35 5 60 G35 3 1000 9.9 7.0 +5040 0.1 (−)*³ S26 35 5 60 G40 0 1000 — — — — 0.1 (−)*³ S27 35 5 60 G40 31000 — — — — 0.1 (−)*³ S28 45 5 50 G23 1 900 10.3 7.0 — 300 0.1 (−)*³S29 55 5 40 G23 0 900 9.6 7.1 — 150 0.1 (−)*³ S30 75 5 20 G23 3 900 10.57.0 — 260 0.1 (−)*³ S31 15 5 80 G36 3 900 9.8 7.0 +70 120 0.1 (−)*³ S3245 5 50 G39 0 900 10.3 7.0 +90 80 0.1 (−)*³ S33 15 5 80 G31 3 900 10.67.0 +80 50 0.1 (−)*³ S34 15 5 80 G28 3 900 10.7 7.0 +60 40 0.1 (−)*³ S3535 5 60 G27 3 900 10.6 6.9 — 650 0.1 (−)*³ S36 35 1 64 G1 2 900 9.8 6.8+40 450 0.1 (−)*³ S37 34 2 64 G1 2 900 9.8 6.8 +35 480 0.1 (−)*³ S38 324 64 G1 2 900 9.9 6.9 +30 580 0.1 (−)*³ S39 31 5 64 G1 2 900 10.0 7.0+20 700 0.1 (−)*³ S40 28 8 64 G1 2 900 10.4 7.2 +10 500 0.1 (−)*³ S41 2610 64 G1 2 900 10.6 7.3 −5 450 0.1 (−)*³ S42 24 12 64 G1 2 900 10.7 7.4−15 400 0.1 (−)*³ S43 21 15 64 G1 2 900 11.2 7.6 −30 400 0.1 (−)*³ S4435 5 60 G2 1 900 10.0 7.2 +10 750 0.1 (−)*³ S45 40 5 55 G6 2 900 10.16.7 +20 660 0.1 (−)*³ S46 30 10 60 G7 3 900 9.8 7.1 −25 700 0.1 (−)*³S47 35 5 60 G8 3 900 9.9 7.2 +15 580 0.1 (−)*³ S48 20 1 80 G9 3 900 9.67.4 +80 470 0.1 (−)*³ S49 35 5 60 G24 3 900 9.8 7.0 — 220 0.1 (−)*³ S5035 5 60 G29 3 900 9.9 7.1 — 340 0.1 (−)*³ S51 35 5 60 G32 3 900 — — — —0.1 (−)*³ *¹TEC represents the term thermal expansion coefficient. *²DIDrepresents the term difference in dimension. *³0.1 (−) means 0.1 orless.

Example 2

An Mg(OH)₂ powder and an Al₂O₃ powder, which are raw materials, wereweighed so as to form a stoichiometric composition corresponding toMgAl₂O₄ and wet-mixed for 16 hours, and the mixture was dried. The driedmixture was fired at 1350° C. for 2 hours and then crushed. The ceramicpowder obtained by the crushing was mixed together with glass powderscomprising the above compositions G1 to G40 in the ratios shown in thefollowing Table 4, and CuO was added to the mixed powders depending onneeds. A solvent, a binder, and a plasticizer were added to the mixedpowders to prepare slurry samples T1 to T29. The slurry samples wereformed into green ceramic sheets having a thickness of 50 μm by a doctorblade method.

Apart from the above green ceramic sheets, the second green ceramicsheets used in Example 1 were separately prepared.

In the same way as in Example 1, insulating ceramic samples wereprepared and then evaluated. In this embodiment, the change ininsulation resistance before and after a high-humidity test was notevaluated and the flexural strength of the insulating ceramic sampleswas measured.

Sample T0 was prepared by firing a layered body comprising the firstgreen ceramic sheets without using the second green sheets. The resultsare shown in the following Table 4.

TABLE 4 Ceramic Powder Glass Firing TEC*¹ Flexural MgAl₂O₄ Mg₂SiO₄Powder CuO Temp. (ppm Strength DID*² (wt %) (wt %) (wt %) Type (wt %) (°C.) deg⁻¹) εr (MPa) Q (%) T0 38 2 60 G3 3 900 9.7 7.0 230 460 0.5 T1 382 60 G3 3 900 9.8 7.0 230 450 0.1 (−)*³ T2 35 5 60 G3 3 900 10.0 7.1 210480 0.1 (−)*³ T3 34 6 60 G3 3 900 10.2 7.1 190 500 0.1 (−)*³ T4 20 0 80G14 3 900 9.7 7.0 210 480 0.1 (−)*³ T5 18 2 80 G14 3 900 9.7 7.0 200 5200.1 (−)*³ T10 50 0 50 G15 0 900 10.0 7.0 250 550 0.1 (−)*³ T11 50 0 50G15 1 900 10.0 7.0 260 580 0.1 (−)*³ T12 60 0 40 G15 0 900 9.9 7.1 255550 0.1 (−)*³ T13 80 0 20 G15 3 1000 10.2 7.0 265 580 0.1 (−)*³ T14 90 010 G15 0 1000 10.3 6.9 230 500 0.1 (−)*³ T15 45 5 50 G15 0 900 10.1 7.1220 600 0.1 (−)*³ T16 40 10 50 G15 0 900 10.0 7.0 180 650 0.1 (−)*³ T1735 5 60 G4 3 900 10.1 7.2 220 460 0.1 (−)*³ T18 35 5 60 G10 3 900 10.47.0 190 530 0.1 (−)*³ T19 35 5 60 G11 3 900 9.8 7.0 190 500 0.1 (−)*³T20 35 5 60 G12 3 900 9.7 7.1 200 520 0.1 (−)*³ T21 35 5 60 G16 3 90010.0 7.0 210 320 0.1 (−)*³ T22 35 5 60 G21 3 900 10.4 7.3 180 420 0.1(−)*³ T23 35 5 60 G22 3 900 10.2 7.3 200 490 0.1 (−)*³ T24 35 5 60 G25 3900 10.8 7.6 230 510 0.1 (−)*³ T25 35 5 60 G30 3 900 10.5 7.3 245 3900.1 (−)*³ T26 35 5 60 G33 3 900 10.2 7.1 230 300 0.1 (−)*³ T27 35 5 60G34 3 900 10.3 7.1 195 450 0.1 (−)*³ T28 35 5 60 G37 3 900 10.2 6.6 80320 0.1 (−)*³ T29 35 5 60 G38 3 900 10.9 8.0 205 60 0.1 (−)*³ ^(*1)TECrepresents the term thermal expansion coefficient. ^(*2)DID representsthe term difference in dimension. ^(*3)0.1 (−) means 0.1 or less.

According to the above embodiments, since the insulating ceramiccompositions of the embodiments include a MgAl₂O₄ ceramic powder andglass powders comprising the above particular compositions, theinsulating ceramic compositions can be fired at a low temperature of1000° C. or less. Thus, the insulating ceramic compositions can be firedtogether with a conductive material comprising a low-melting metal suchas silver and copper and such a conductive material can be used forinternal electrodes, thereby achieving ceramic multilayer substrateshaving excellent high-frequency characteristics.

In particular, since the insulating ceramic compositions according tothe first embodiment include the MgAl₂O₄ ceramic powder containingtitanium oxide (TiO₂) and the glass powders comprising the aboveparticular compositions, insulating ceramics obtained by firing theinsulating ceramic compositions have high mechanical strength and alarge Q-factor at high frequencies. Thus, ceramic multilayer substrateshaving excellent high-frequency characteristics and high mechanicalstrength can be manufactured.

Since the insulating ceramic compositions according to the secondembodiment include the MgAl₂O₄ ceramic powder of which part is replacedwith Mg₂SiO₄ and the glass powders comprising the above particularcompositions, insulating ceramics obtained by firing the insulatingceramic compositions have high mechanical strength, a large thermalexpansion coefficient, and a large Q-factor at high frequencies. Thus,ceramic multilayer substrates having excellent high-frequencycharacteristics, high mechanical strength, and a large thermal expansioncoefficient can be manufactured.

INDUSTRIAL APPLICIABILTY

According to the present invention, ceramic electronic components havinghigh mechanical strength and excellent high-frequency characteristicscan be achieved.

1. An insulating ceramic composition comprising a ceramic powdercomprising spinel (MgAl₂O₄), a glass powder comprising 30-60% by mole ofsilicon oxide on the basis of SiO₂ and 20-55% by mole of magnesium oxideon the basis of MgO, and wherein the composition contains titanium oxideor the ceramic contains Mg₂SiO₄.
 2. An insulating ceramic compositionaccording to claim 1, wherein the ceramic powder comprisies spinel(MgAl₂O₄) and Mg₂SiO₄.
 3. The insulating ceramic composition accordingto claim 2, wherein the Mg₂SiO₄ is 15% by weight or less of the combinedweight of the spinel and the Mg₂SiO₄.
 4. The insulating ceramiccomposition according to claim 2, wherein the glass powder furthercontains 20% by mole or less of boron oxide on the basis of B₂O₃.
 5. Theinsulating ceramic composition according to claim 2, wherein the glasspowder further contains 30% by mole or less of at least one oxideselected from the group consisting of CaO, SrO, BaO, and ZnO.
 6. Theinsulating ceramic composition according to claim 2, wherein the glasspowder further contains 10% by mole or less of aluminum oxide on thebasis of Al₂O₃.
 7. The insulating ceramic composition according to claim2, wherein the glass powder further contains 10% by mole or less of atleast one alkaline metal oxide selected from the group consisting ofLi₂O, K₂O, and Na₂O with respect to 100% by mass of the glass powder. 8.The insulating ceramic composition according to claim 2 furthercomprising 3% by weight or less of copper oxide on the basis of CuO withrespect to the total ceramic powder and glass powder content.
 9. Theinsulating ceramic composition according to claim 2, wherein the ratioof the ceramic powder content to the glass powder content is 20:80 to80:20 on a weight basis.
 10. An insulating ceramic comprising a firedinsulating ceramic composition according to claim
 2. 11. A ceramicmultilayer substrate comprising a plurality of ceramic layers and aconductive wire disposed on at least one of the plurality of ceramiclayers, wherein the plurality of ceramic layers include an insulatingceramic layer comprising the insulating ceramic according to claim 10.12. The ceramic multilayer substrate according to claim 11, wherein theplurality of ceramic layers further include a dielectric ceramic layerthat is disposed on at least one principal face of the insulatingceramic layer and that has a dielectric constant higher than that of theinsulating ceramic layer.
 13. A ceramic electronic component comprisingthe ceramic multilayer substrate according to claim 11 and a circuitelement that is mounted on the ceramic multilayer substrate and iselectrically connected to the conductive wire.
 14. A ceramic electroniccomponent comprising the ceramic multilayer substrate according to claim13, wherein the circuit element is at least one of an inductor and acapacitor.
 15. A method for manufacturing a ceramic multilayer substratecomprising the steps of layering first green ceramic sheets comprisingthe insulating ceramic composition according to claim 2 to prepare alayered body, providing a second green ceramic sheet having a sinteringtemperature different from that of the first green ceramic sheets ontoat least one principal face of the layered first green ceramic sheets,and firing the layered body including the first green ceramic sheetstogether with the second green ceramic sheet.
 16. The method formanufacturing a ceramic multilayer substrate according to claim 15,wherein the second green ceramic sheet is not substantially sintered atthe sintering temperature of the first green ceramic sheets.
 17. Themethod for manufacturing a ceramic multilayer substrate according toclaim 16, wherein the layered body including the first green ceramicsheets is fired at 1000° C. or less together with the second greenceramic sheet.
 18. An insulating ceramic composition according to claim1, wherein the titanium oxide is present.
 19. The insulating ceramiccomposition according to claim 18, wherein the titanium oxide iscontained in the ceramic powder.
 20. The insulating ceramic compositionaccording to claim 19, wherein the content of the titanium oxide is0.5-15% by weight with respect to the total ceramic powder and glasspowder content.